Seed Germination Virtual Lab: Conditions and Flower Parts

This seed germination virtual lab runs the GCSE and IGCSE practical on the conditions seeds need to germinate. Students set up five tubes of 20 cress seeds: a control, and tubes without water, without oxygen, in the dark, and in a cold, dark fridge. They count the germinated seeds every day for a week, plot percentage germination against time and decide which conditions are needed. A second part dissects a flower and a soaked bean seed beside a ruler. A week of germination takes seconds, so one lesson covers both practicals.

Curriculum links

• Cambridge IGCSE Biology 0610, topics 16.2–16.3 (sexual reproduction in plants): flower structure, and the investigation of the environmental conditions that affect germination.
• AQA GCSE Biology: enzymes, temperature and aerobic respiration, applied to germination.
• IB Biology D3.1 (reproduction) and Australian Curriculum Science Year 9 (AC9S9U02).

Simulic is not affiliated with or endorsed by Cambridge, AQA, the IB or any exam board.

Before the lab (5 min)

Ask students to commit to a prediction, on paper or as question 1 of the class link:

"Five tubes of cress seeds are kept for a week. A has water, oxygen, light and 20 °C. B has no water, C no oxygen, D is in a fridge, and E is in the dark at 20 °C. In which tubes will most seeds germinate?"

Many students leave out tube E, thinking seeds need light. Don't correct them yet.

Method in the simulation

Part 1: germination (20 min)

1. Open the Germination tab. Keep Room temperature at 20 °C, Days to record at 7 and the five tubes as set (A is the control).
2. Press Start. The table records the percentage of seeds germinated at the end of each day, and the graph plots it.
3. Copy the day-by-day results for tubes A to E into your table.
4. Set Room temperature to 10 °C (this resets the tubes) and press Start again. Note the first day tube A reaches 50%.

Tube	Water	O₂	Light	T (°C)	Day 1	Day 2	Day 3	Day 7
A	yes	yes	yes	20
B	no	yes	yes	20
C	yes	no	yes	20
D	yes	yes	no	4
E	yes	yes	no	20

Part 2: flower and seed dissection (15 min)

5. Open the Dissect tab with Specimen "Insect-pollinated flower". Press Remove next layer until the button changes to Cut open the ovary, and press that too.
6. Count each part, read the lengths on the ruler and work out the means. Tick Show measurements to check.
7. Repeat with the wind-pollinated flower and the soaked bean seed.

Expected results

About 90% of the seeds are viable and each seed needs a slightly different amount of warmth, so every run differs a little. The ranges show where 9 runs in 10 fall.

Tube	Day 1	Day 2	Day 3	Day 7
A, 20 °C	0–10%	50–85%	75–100%	80–100% (mean 90%)
B, no water	0	0	0	0
C, no oxygen	0	0	0	0
D, fridge 4 °C	0	0	0	0 (rarely 5%)
E, dark, 20 °C	like A	like A	like A	like A

• Tubes A and E give similar results, so light is not needed to germinate. The seedlings in E are tall and pale yellow (etiolated).
• At 10 °C, tube A first reaches 50% on day 4 or 5, compared with day 2 at 20 °C. At 25 °C it is fastest; at 35 °C it is slower again, and at 40 °C nothing germinates.
• Dissection: the insect-pollinated flower has 5 sepals (about 8 mm), 5 petals (about 15 mm), 10 stamens (about 9 mm) and 1 carpel (about 11 mm) with 4 to 8 ovules; one run gave means of 8.6, 15.8, 9.3 and 12.0 mm and 8 ovules. The grass flower has 2 bracts, 3 stamens and feathery stigmas. The bean seed has a testa, 2 cotyledons and an embryo (plumule and radicle).

Questions for students

1. (Prediction, asked again after the lab) In which tubes will most seeds germinate?
2. Tube D is cold and dark. Which tube should it be compared with to test the effect of temperature?
3. At 20 °C, what percentage of the seeds in tube A have germinated at the end of day 7?
4. At 10 °C, on which day does tube A first reach at least 50%?
5. Explain why the seeds in tubes B and C do not germinate.

Answers for teachers: (1) A and E. (2) Tube E, which is also dark, so temperature is the only difference. (3) About 90% (accept 60 to 100). (4) Day 4 or 5 (at 20 °C it is day 2). (5) Without water the seed cannot swell, and its enzymes stay inactive, so the food store is not broken down. Without oxygen there is no aerobic respiration to release energy for growth.

Common misconceptions

• "Seeds need light to germinate." Most seeds, including cress, do not. Light matters for the seedling afterwards, which is why the seedlings in tube E are yellow.
• "The fridge tube tests temperature alone." Tube D is cold and dark. Compare it with E.
• "Warmer is always faster." Germination speeds up to an optimum (about 25 °C here), then slows, because the enzymes work best at an optimum temperature.

Extension

• Change one tube in the table, for example tube C to 30 °C with oxygen, and predict its curve first.
• On the Pollination tab, follow a pollen tube to the ovule and double fertilization, then press Pollinate 10 flowers with self-pollen on a self-incompatible plant.

FAQ

Can the class link open straight on the Germination tab?

Yes. On the Share page, pin Screen to "Germination" in the link's starting values. You can also pin Room temperature and Days of germination record. Otherwise the first step tells students to open the tab.

Why do two students get different percentages?

Each run draws new seeds: about 1 in 10 is not viable, and each needs a different amount of warmth. That is why question 3 accepts a range.

Does this replace growing real seeds?

No. Start real tubes on Monday and run the simulation the same day, then check the real tubes later. See virtual labs vs physical labs.

Related simulations and guides

Respirometer – oxygen uptake of germinating seeds Photosynthesis – counting oxygen bubbles in pondweed

To measure the oxygen that germinating seeds use, see the respirometer virtual lab.